AsianScientist (Mar. 17, 2017) – In a breakthrough in the miniaturization of storage media, researchers have successfully stored one bit of digital information in a single atom. These findings, by Professor Andreas Heinrich, the newly appointed director of the Center for Quantum Nanoscience at the Institute of Basic Science South Korea, has been published in Nature.
Disks coated with a magnetized layer of metal allow our computers to store files in the form of bits, each with the value of either 1 or 0. One direction of magnetization corresponds to the 0 bit, the other direction to the 1 bit. At the moment, small areas of the disk—of around a million atoms—correspond to each digital bit of information.
In this study, scientists worked with a tool called scanning tunneling microscopy (STM) which has a special tip that enables the user to view and move individual atoms, as well as to apply a pulse of electrical current to them. They used this electric pulse to change the direction of magnetization of individual holmium atoms. By doing that, the team could write a memory of either 1 or 0 in a single holmium atom, as well as swap the two.
A quantum sensor, designed by Heinrich’s team and currently unique worldwide, was used to read the memory stored in the holium atom. It consists of an iron atom placed next to the holmium atom. By combining the quantum sensor with tunnel magnetoresistance, the researchers could observe that holmium maintains the same magnetic state stably over several hours.
When the researchers tried to use two holmium atoms instead of one, they made another surprising discovery. Placing holmium atoms even one nanometer apart did not impact their ability to store information individually. This came as a surprise, since it was expected that the magnetic field from one atom would impact its neighbor. To put this scale into perspective, if a nanometer were blown up to the diameter of a typical human hair, the hair would have a diameter equivalent to the length of a school bus in comparison.
In this way, the scientists could build a two-bit device with four possible types of memory: 1-1, 0-0, 1-0 and 0-1 clearly distinguished by the iron sensor.
Moore’s Law predicted that the amount of data that can be stored on a microchip would double every 18 months and indeed this happened for decades. However, as devices becomes smaller and smaller, the closeness of adjacent atoms create new interfering quantum properties and cause problems. This impossibility of keeping up with further miniaturization, brought experts to talk about the death of Moore’s Law.
Interestingly, holmium atoms seem to escape this fate, for reasons that are still unknown.
“There are no quantum mechanical effects between atoms of holmium. Now we want to know why,” Heinrich said. “We have opened up new possibilities for quantum nanoscience by controlling individual atoms precisely as we want. This research may spur innovation in commercial storage media that will expand the possibilities of miniaturizing data storage.”
The article can be found at: Natterer et al. (2017) Reading and Writing Single-Atom Magnets.
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Source: Institute for Basic Science.
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